Hookes type universal joints are well known. Such a joint connects to the drive shaft of rear wheel drive motor vehicles and is often visible on medium duty trucks. A central "+" shaped element is pivotally connected at opposed distal ends to corresponding "Y" shaped yokes. The joint will transmit power at up to about a 35 degree angle and requires no external housing. Hookes universal joints work most smoothly when used in pairs.
U.S. Pat. No. 4,768,995 to Mangiavacchi shows a typical complete Hookes joint assembly.
U.S. Pat. No. 2,750,766 to Griswold shows an assembly of swiveling and sliding elements within a housing to form a 90.degree. angle between two shafts. A central plate is pivotably attached at each end to slotted cylinders. The cylinders oscillate within holes cross drilled in the ends of the drive shafts.
U.S. Pat. No. 3,533,248 to Freund shows an assembly of slotted and tabbed plates to form a series of two Hookes universal joints. The drive shafts have slotted ends to receive end plates of the assembly. The plates are secured to the shafts by pins.
Another mechanism to transmit power at an angle is a bevel gear set. In this arrangement, the angle of transmission is fixed although, unlike universal joints, a drive ratio other than 1:1 may be used.
In contrast to prior art universal joints, the present invention has drive shafts rotatably mounted within a rigid housing with their rotational axes fixed at a pre-determined relative angle. The end plates are held to the drive shafts by spring latches built into the profile of the end plate.
In a preferred embodiment each drive shaft has an axial hexagonal recess so that a hexagonal shank may connect to the drive shaft from outside the housing. The drive shafts are identical but one has an input shank fitted in the recess. The input shank has a circumferencial groove to receive a rib of the housing so that the shank is held from pulling out of the recess.
The mechanism in a preferred embodiment comprises two sequential Hookes universal joints to produce double the angle of single such joint. The components of the universal joint are made from stamped steel. The steel components engage each other by simple pivoting contact. The contact occurs along a single line at each linkage point, where the linkages are in the form of tabs and slots.
Since there is minimal sliding at the pivoting linkage point, the drive system of the present invention is low friction and efficient.
The universal joint of the present invention is intended to operate at a fixed angle and to be grasped firmly by a user's hand. It is therefore fully contained in a rigid housing. The housing serves a further important function of holding the universal joint components together against tensile forces. The engagements of the metal plates must be held together by outside means or the tabs will pull out of the corresponding slots. The housing therefore holds rotating drive shafts and an input shank securely while the shafts support the end yokes of a universal joint assembly.
The angle drive assembly of the present invention may be used as an accessory tool for screwdriving and drilling, or as a sub assembly within a larger machine or device where an efficient low cost means to change a drive shaft angle is required.
The present invention addresses improved means to hold elements of the assembly together. Specifically a method to retain an input shank and an end linkage to a drive shaft is disclosed.